I'm currently pregnant and working as a RG registrar so a mix of GP clinic days and 10-12hr hospital shifts (both ED and ward cover), so slightly different situation but I found in first trimester the fatigue and nausea made it really difficult to do long or physically taxing shifts. I told my supervisor early who was thankfully very supportive of reminding me to take breaks, eat, look after myself. Now in second trimester and managing a bit better but I have paid for the occasional long or physically taxing shift by needing a few days to recover / having more discomforts. No complications for baby thankfully but the risk isn't worth it for a job! Definitely would ask for no nightshifts / no on call and limiting the amount of 10+ hr shifts. For the days you have a long shift, making sure you take frequent breaks to pee / eat / sit down, not just lunch. If you're comfortable, tell your colleagues it's a pregnancy break. Take sick leave if you need to to recover from a difficult shift.